alternate vs irregular

alternate

adj
  • Happening by turns; one following the other in succession of time or place; first one and then the other (repeatedly) 

  • Other; alternative. 

  • Distributed singly at different heights of the stem, and at equal intervals as respects angular divergence 

  • Designating the members in a series, which regularly intervene between the members of another series, as the odd or even numbers of the numerals; every other; every second. 

noun
  • A substitute; an alternative; one designated to take the place of another, if necessary, in performing some duty. 

  • A replacement of equal or greater value or function. 

  • A proportion derived from another proportion by interchanging the means. 

  • That which alternates with something else; vicissitude. 

  • Figures or tinctures that succeed each other by turns. 

verb
  • To vary by turns. 

  • To perform by turns, or in succession; to cause to succeed by turns; to interchange regularly. 

  • To perform an alternation (removal of alternate vertices) on (a polytope or tessellation); to remove vertices (from a face or edge) as part of an alternation. 

  • To happen, succeed, or act by turns; to follow reciprocally in place or time; followed by with. 

irregular

adj
  • not regular; having sides that are not equal or angles that are not equal 

  • without symmetry, regularity, or uniformity 

  • rough 

  • whose faces are not all regular polygons (or are not equally inclined to each other) 

  • nonstandard; not conforming to rules or expectations 

  • not following the regular or expected patterns of inflection in a given language 

noun
  • A soldier who is not a member of an official military force and who may not use regular army tactics. 

  • One who does not regularly attend a venue. 

How often have the words alternate and irregular occurred in a corpus of books? (source: Google Ngram Viewer )